TF damage bug?

There is some issue with my damage registering on TF. I gold card + Qd a kha-zix who had no MR outside of merc treads and barely did 1/4 of his health.

My gold card damage was: 45+98+268. He said it did 126 damage to him. At the time I had full stacked roa, lich, dcap, and dorans.

This happened several times, the first time it happened we both noticed it and agreed it was quite weird. Then it happened a 2nd a 3rd time.